How can I make emacs highlight lines that go over 80 chars?

Question

I know there are solutions to making emacs show the 80 line column, but I don't want that sort of visual disturbance. I'd just like to make it highlight a line if it's over 80 characters.

Answer 1

Another easy option is to run highlight-lines-matching-regexp on the expression .\{81\}.

Every line with 81 characters or more will be highlighted with the color of your choice.

Answer 2

See whitespace-mode -- it's now part of Emacs, and can do much more than highlighting just long lines. (But of course can be used to do only that.)

Answer 3

Here's my config from Emacs Dev Kit:

;; whitespace-mode
;; free of trailing whitespace and to use 80-column width, standard indentation
(setq whitespace-style '(trailing lines space-before-tab
                                  indentation space-after-tab)
      whitespace-line-column 80)

Basically you need just the last bit, but I find the other settings quite useful (I hate tabs and trailing whitespaces).

Answer 4

Try highlight-80+.el. You can acquire it from here.

To install it, just add the following to your .emacs:

(add-to-list 'load-path "/path/to/highlight-80+")
(require 'highlight-80+)

You can then enable it via:

M-x highlight-80+-mode